Interconnecting conductive links

ABSTRACT

Conductive links are provided between conductive materials, e.g., metals, separated by a non-conductive material, e.g., a silicon based glass material. In a preferred embodiment a single pulse of laser energy is applied to at least one of the conductive materials to produce mechanical strain therein which strain initiates a fracturing of the non-conductive material so as to provide at least one fissure therein extending between the conductive materials. The laser energy pulse further causes at least one of the conductive materials to flow in such fissure to provide a conductive link between the conductive materials. Preferably, the non-conductive material is formed in layers such that an interface between the layers controls the fissures.

RELATED APPLICATION(S)

This application is a Continuation of application Ser. No. 09/285,526,now U.S. Pat. No. 6,191,486 filed on Apr. 2, 1999, which is aContinuation of application Ser. No. 08/704,505 now U.S. Pat. No.5,920,789 filed on Oct. 3, 1996, which is the U.S. National Stage ofInternational Application No. PCT/US95/03107, filed on Mar. 9, 1995,published in English, which is a Continuation-in-Part of applicationSer. No. 08/370,004, now U.S. Pat. No. 5,585,602 filed on Jan. 9, 1995;and application Ser. No. 08/320,925, now U.S. Pat. No. 5,940,727 filedon Oct. 11, 1994, which is a Continuation-in-Part of application Ser.No. 08/209,997, now U.S. Pat. No. 5,861,325 filed on Mar. 10, 1994. Theentire teachings of the above applications are incorporated herein byreference.

GOVERNMENT SUPPORT

The invention was supported, in whole or in part, by a grant NumberF19628-90C-0002 from the Department of the Air Force. The Government hascertain rights in the invention.

INTRODUCTION

This invention relates generally to techniques for producinginterconnecting conductive links and, more particularly, to a uniqueprocess for providing conductive links between two conductive materialshaving a non-conductive material positioned between them.

BACKGROUND OF THE INVENTION

Configurations of interconnected arrays of conductive elements, as used,for example, in programmable logic gate arrays, requires the formationof conductive links, or paths, between selected conductive elements in amanner which produces relatively low resistance links between them.Techniques for producing such low resistance conductive links have beendeveloped using either electrical or laser linking and cuttingprocesses.

The latter laser processes have been preferred for certain applicationsbecause they provide permanent links and require no programming wiringor high voltage switching on the chip. Laser programmable techniqueshave the potential for providing higher performance and greater linkdensity than electrical techniques if the linking device itself issufficiently small. Ultimately the minimum size laser link would be asimple crossing of two wires. However, up to now insofar as is known, asuccessful process does not exist for providing such links. A primaryconcern when using any linking technology is the ability to use standardprocessing for the metal lines on the insulation. More specifically,this means the ability to integrate laser restructurable elements usingstandard silicon based MOS processing without the need to incorporateadditional steps. Lateral links, which produce conductive links usingsilicon diffusion, have been used for some time to achieve compatibilitywith CMOS processing, as disclosed in U.S. Pat. No. 4,455,495, toMasuhara et al. and in U.S. Pat. No. 4,937,475, issued to F. M. Rhodeset al. on Jun. 26, 1990. These techniques require large areas to focusthe laser to the substrate and have high resistance.

Other recent exemplary techniques have been proposed using laser linkingprocesses for interconnecting metal layers at different levels. One suchtechnique is disclosed in U.S. Pat. No. 5,166,556 issued on Nov. 24,1992 to F. Shu et al. in which a laser beam is applied to an uppertitanium metal layer at the location at which a link is desired to bemade with a lower titanium layer. Laser power is supplied at asufficient level to cause a chemical reduction reaction between thetitanium layers and the intermediate silicon dioxide insulating layer soas to produce a conductive compound between the titanium layers whichacts as an electrically conductive circuit therebetween. Such techniquerequires additional non-standard process steps and produces highresistance links and, hence, low performance.

U.S. Pat. No. 4,810,663 issued to J. I. Raffel et al. on Mar. 7, 1989discusses a technique in which a diffusion barrier layer is placedbetween each metal layer and the insulation layer and the link region isexposed to a low power laser for a relatively long time (i.e., arelatively long pulse width) to cause the metals to alloy with thediffusion and insulating layers to form the desired conductive link.Such technique requires a relatively long laser power pulse output usinga relatively complicated diffusion barrier/insulation structure so as toproduce an opening in the upper layer to permit the energy to be appliedto the barrier and insulating layers to produce the desired alloyingoperation.

A further technique has been proposed to provide lateral links betweenmetals substantially at the same surface or plane as discussed in U.S.Pat. No. 4,636,404 issued to J. I. Raffel et al. on Jan. 13, 1987. Againrelatively long pulses are applied to the general region between themetals so as to cause the metals to form an aluminum doped silicon link.

In a recent article “Laserpersonalization of Interconnection Arrays forHybrid ASIC's of M. Burnus et al., IEEE International Conference onWafer Scale Integration, 1993, a laser beam is used to providesufficient power to blast a hole through an upper metal layer so as toform an opening at the link region. Multiple laser pulses of high energydensity are used to create the opening and to remove the insulatinglayer between the metal elements. The multiple pulses also producemolten aluminum which spreads along the walls of a crater that is formedwhen the insulating layer is removed beneath the opening. Such aluminumflow along the crater walls produces a tube-like aluminum contact bodybetween the upper and lower aluminum layers.

The article “Laser Programmable Vias for Reconfiguration of IntegratedCircuits” by Rouillon-Martin et al. in Optical Microlithography andMetrology for Microcircuit Fabrication, 1989, discloses a techniquewhich performs a similar operation to that discussed in the above Burnuset al. article in which the opening is made much smaller in diameter byusing multiple pulses of a relatively highly focused laser beam.

It is desirable to devise a laser linking process which produces a linkstructure between any two metal layers which can be fabricated in amanner which is compatible with standard MOS processes and whichprovides high performance (low resistance) and high density (small area)links. Such process should use relatively low laser power and provideself-contained links with low peripheral damage at the link sites.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention, in a linking processan energy producing device, e.g., a laser, applies a single pulse ofsufficient energy to at least one of two conductive materials which areto be linked, and which have a non-conductive material between them, soas to produce mechanical strain in at least one of the conductivematerials. The strain that is produced initiates a fracturing of thenon-conductive material so as to provide at least one fissure thereinwhich extends between the conductive materials. The single energy pulseapplied by the energy producing device further causes a portion of atleast one of the conductive materials to flow in the at least onefissure to provide at least one conductive link between the conductivematerials. In most cases, an effective fissure extends from a point ator near an edge of at least one of the conductive materials to the otherconductive material.

Preferably the non-conductive material is a silicon based dielectricsuch as silicon oxide or silicon nitride. The fracture and conductivelink is preferably obtained with a pulse of energy of less than 1microjoule and a pulse duration of less than 1 microsecond. The mostpreferred pulse duration is in the range of 1 to 10 nanoseconds.

In the preferred embodiment, the first and second conductive materialsare metals lying substantially in the same plane and the fissure extendsgenerally laterally between the first and second conductive materials.By forming the non-conductive material in layers, an interface betweenthe layers can control the fracturing. The fracture may be formed alongor be limited by the interface. Preferably, an interface of hardmaterial over softer material is provided at a level above theconductive materials.

In another embodiment of the invention, an upper metal layer isdeposited on the non-conductive material in a manner so as to provide apreformed opening at the desired link site. A single pulse of energy canthen be used to be effectively applied to the lower metal layer at thelink site so as to produce the mechanical strain required to initiatethe fracturing of the dielectric or insulating material, as discussedabove. In a still further embodiment of the invention, if a preformedopening is used in the upper metal layer, a single laser pulse of energymay be used to provide a desired chemical reaction, or desired alloying,or a desired removal of the dielectric to create a crater therein,without having to produce an opening through the upper metal layer.Accordingly, by the use of such a preformed opening a conductive linkmay be formed from fracturing or from a chemical reduction reactionprocess, an alloying process, or the flow of metal in a crater formed inthe dielectric which has been removed at the link site. Thus, in somecases the use of the preformed opening may not require a fracturing ofthe dielectric material between the metal elements.

In accordance with a preferred implementation of the invention, a firstpattern of first preformed conductive elements and a second pattern ofsecond conductive elements are provided on a substrate and lateralconductive links are formed at a single level between selected ones ofthe first and second conductive elements so as to provide a plurality ofdesired conductive paths. As used herein, the term “level” is intendedto include embodiments wherein the surfaces of the elements involved inthe link lie at substantially the same level, whether or not theelements themselves are formed or deposited on the same planar surface.In one embodiment thereof, for example, a first pattern of conductiveelements is formed at a first level while a second pattern of secondconductive elements is such that it has portions of its conductiveelements at two levels, i.e., first portions thereof being at the samelevel as the first conductive elements and other portions thereof beingat another second level below the first level. Lateral conductive linksare then formed at a single level between selected ones of the firstconductive elements and selected ones of the portions of the secondconductive elements that are at the same level. In another embodiment,for example, the first and second patterns of conductive elements areall formed at the same level and lateral links are formed at such level.In addition, appropriate cuts can also be made to separate, asnecessary, the conductive paths that are so formed.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

The invention can be described in more detail with the help of theaccompanying drawings wherein

FIG. 1 shows a plan view of an embodiment of the invention depicting anexemplary site at which a conductive link is to be produced;

FIG. 2 shows a view in section along the lines 1-2 of the link siteshown in FIG. 1;

FIG. 3 shows a view in section of another embodiment of the inventiondepicting a site at which a conductive link has been produced inaccordance with the invention;

FIG. 4 shows a view in section of another embodiment of the inventiondepicting a site at which a lateral conductive link is to be producedbetween metal elements, generally in the same plane;

FIG. 5 shows a view in section of the site of FIG. 4 in which aconductive link is provided in accordance with the invention;

FIG. 6 shows a view in section of another embodiment of the inventiondepicting a site using an alloying or chemical reaction in thedielectric between the metal layers thereof;

FIG. 7 shows a view in section of another embodiment of the inventiondepicting a site at which a conductive link is provided by forming acrater in the dielectric material between the metal layers thereof; and

FIG. 8 shows a view in section of another embodiment of the invention inwhich a lateral conductive link is to be provided;

FIG. 9 shows a view in section of the embodiment of FIG. 8 in which alateral link has been provided;

FIG. 10 shows a view in section of another embodiment of the inventionin which a lateral conductive link is to be provided;

FIG. 11 shows a view in section of the embodiment of FIG. 9 in which alateral link has been provided;

FIG. 12 shows a view in section of another embodiment of the inventionin which a lateral conductive link is to be provided; and

FIG. 13 shows a view in section of the embodiment of FIG. 12 in which alateral link has been provided;

FIG. 14 depicts patterns of exemplary conductive elements in which linksand cuts can be provided to form desired conductive paths;

FIG. 15 depicts in vertical section a portion of the pattern of FIG. 14;

FIG. 16 depicts exemplary conductive paths that are formed in thepatterns of FIG. 14 using the technique of the invention;

FIG. 17 depicts other patterns of exemplary conductive elements in whichlinks and cuts can be provided to form desired conductive paths; and

FIG. 18 depicts exemplary conductive paths that are formed in thepatterns of FIG. 17 using the technique of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As can be seen in FIGS. 1 and 2, a lower conductive material in the formof a metal element 10 lies generally in a first plane 11 at a lowerlevel with reference to an upper conductive material in the form of ametal element 12 which lies in generally a second plane 13 above metalelement 10. In the particular embodiment depicted, a non-conductive(insulating) material 14, such as a glass dielectric, effectivelyencloses metal elements 10 and 12 and provides a layer 14A thereofbetween such elements. In a preferred embodiment of the process of theinvention a preformed opening 15 is provided in metal element 12 at thedesired link site. As shown, in this embodiment, the opening 15 is widerthan the width of the metal element 10. The metal elements and theinsulating material are mounted on a suitable substrate 16 such as afurther glass or other appropriate substrate material. It is desired toprovide an electrically conductive link between the metal elements 10and 12.

A link site shown in FIG. 3 is similar to that depicted in FIGS. 1 and2, except that the width of the lower metal layer 10 is co-extensivewith the width of upper metal layer 12.

As shown in FIG. 3 an energy producing device, such as a laser (notspecifically shown in the Figure), is positioned above the link site soas to apply laser energy, depicted by arrows 17, through the structureof FIG. 3. at the opening 15 thereof. Such laser energy is applied inthe form of a single pulse of energy, as discussed in more detail below.The energy of the single pulse so applied is at a sufficient power levelthat it causes either or both metal elements 10 and 12 to become heatedso that mechanical strains are produced therein and both elementsthermally expand at portions thereof where the energy is applied, asshown by the exaggerated thermally expanded portions 10A and 12Athereof.

The mechanical strains thereby initiate a fracturing of the glassdielectric material 14 so as to produce one or more fissures 18 therein,particularly in the region 14A thereof. While the fissures which are soproduced may extend throughout the material 14 one or more of them willextend from metal element 12 to metal element 10, normally one or moreof the latter fissures extending from a position at or near at least oneedge 19 of metal element 12, as shown by exemplary fissure 18A. Thelaser energy further causes metal from at least one of the metal layers,e.g., the layer with the lower melting point, to flow from such layerinto the fissure so as to contact the other layer, as shown. Similarfissures and at least one conductive link between layers 10 and 12 wouldbe produced in the structure of FIGS. 1 and 2 as shown by exemplaryconductive links 18A in FIG. 2. With the opening 15 wider than theconductive element 10, each link 18A extending from near an edge of theconductive element 12 to near an edge of the conductive element 10 has alateral component.

In a particular embodiment of the invention, used for the link siteshown in FIG. 3, for example, a continuous wave argon ion laser wasapplied to the link site, which had a site area of 4 μm×4 μm and anopening area of 2 μm×2 μm, via a suitable electro-optical shutter,shutter driver circuitry, and associated optical elements, suchstructures and operation being well known to those in the art. The metallayers were separated by a layer of a silicon oxide dielectric having alayer thickness of 0.75 μm. between the metal layers. The laser producedsingle pulses of laser output power of about 1.0 watts having a pulsewidth from about 1 microsecond (μs) to about 3 μs. The shutter wasarranged to provide laser power rise and fall times, i.e., between about10% to 90% of full power, of about 200 nanoseconds (ns). The laseroutput pulse was formed to provide a minimum beam diameter, through amicroscope objective lens producing a 1/e radius of about 1.0micrometers (μm).

Single pulses of such pulse widths were found to provide a highprobability of producing one or more satisfactory conductive links,i.e., a failure rate of less than one in approximately fifty links, inthe above embodiment. Further increases in the pulse width did notappear to provide any significant improvement in link probability andpulse widths between about 1 to 3 microseconds appeared to be adequatefor the structure shown. The necessary energy dose was nearly 1 μjuole.In some cases it is believed that even smaller pulse widths can be used,e.g., greater than about 1 nanoseconds (ns) so long as they providesufficient energy to cause the fracturing and metal flow required.

Moreover, in the above described particular embodiment process it wasfound that using more than a single pulse also did not appear to improvethe probability of forming one or more conductive links and that, if asingle pulse failed to produce at least one link, the use of additionalpulses did not tend to do so.

In the particular embodiment discussed above it was also found thatlaser output power in a range from about 0.5 to 1.0 watts proved to besufficient to provide one or more fissures to form the desiredconducting links. For example, a peak laser output power of 0.72 wattsyielded 98.2% out of 1021 link attempts using pulse widths of onemicrosecond (μs). The differences in linking probabilities, when thepower used was varied from 0.6 to 0.72 watts, for example, using pulsewidths of 2 μs and 3 μs, appeared to be relatively insignificant. It isbelieved that further improvement will occur by scaling theconfiguration of FIGS. 1 and 2, for example, to provide a link site areaof 4 μm×4 μm, or smaller, such that a failure rate of less than 1 in10000 links should be achieved.

Although a laser is the preferred energy source, other energy sourceswhich introduce sufficient thermal energy into the conductive elementsto cause the thermal expansion may be used. For example, the inventionmay be implemented in a voltage programmable environment. Even where aradiant energy source such as a laser is used, a wide range ofwavelengths may be used. It is only necessary that the energy beabsorbed by the conductive material. Absorption can be enhanced bytreating the conductive metal layer as by providing a thin titaniumlayer on the aluminum.

Although a wide range of energy levels and pulse durations may be used,to maintain the fracturing mode of linkage it is important that not toomuch energy be applied. If too much energy is applied, linkage may stillresult from ablation of the non-conducting layer and the molten flow ofmetal along the walls of the resultant crater. However, such processeshave a disadvantage of damaging the upper passivation layer of thestructure.

The above dielectric fracturing technique for providing vertical linksbetween upper and lower metal layers can also be used to producehorizontal, or lateral, links between metal elements lying insubstantially the same plane, as shown in FIGS. 4 and 5. As seentherein, a pair of separated metal elements 20 and 21 are enclosed in adielectric (e.g., a silicon based glass or polymer) material 22. A laserenergy pulse 25 is applied to the region 23 between the metals. Thelaser pulse produces mechanical strains in the metal elements so thatthey tend to expand so as to provide stresses concentrated at thecorners thereof adjacent region 23, as shown by expanded regions 20A and21A. Such expansions initiate a fracturing of the dielectric material 22so as to produce one or more fissures therein, at least one of whichwill extend from one metal element 20 to the other metal element 21, asshown by exemplary fissures 24. Metal from at least one of the metalswill tend to flow through the at least one fissure to form a conductivelink between metals 20 and 21, as shown by exemplary fissure 24A.

The lateral link has several advantages over the vertical link. With thewindowed vertical link of FIGS. 1-3, for example, the laser spot sizeshould be limited in order to pass through the window without beingabsorbed primarily by the upper metal layer. Further, positioningtolerance of the laser is more critical to avoid radiating the upperlayer. With the lateral link, the spot should be wide enough to heat themetal to either side of the gap. Further, because the metal is thermallyconductive, the spot size can be considerably larger than the gap size.Accordingly, the lateral approach is more scalable since the gap sizecan be made as small as lithographically possible with significanttolerance in laser beam diameter and position. Further, the lateral linkis particularly suited to applications such as flat panel displays whichrequire a single level of metal.

Another embodiment of the invention can also be used for forminghorizontal, or lateral, links between metal elements lying insubstantially the same plane, as shown in FIGS. 8 and 9. As seentherein, a pair of separated metal elements 40 and 41 are positioned ona first dielectric (e.g., a silicon oxide glass or polymer) material 42and embedded in a second dielectric (e.g., a silicon nitride glass orpolymer) material 43 above the first dielectric material 42.Accordingly, an interface is formed at the adjacent surfaces of thedielectric materials a portion 44 of the interface being formed betweenthe metal elements 40 and 41. Energy in the form of one or more laserpulses 45, for example, is applied generally to the region 46 betweenthe metal elements 40

and 41 particularly so as to be applied to the ends of the metalelements.

The mechanical strength characteristics of the dielectric materials aredifferent and the thermal expansion coefficients of the metal elementsare relatively higher than the thermal expansion coefficients of thedielectric materials. Accordingly, when such energy is applied, thermalenergy is absorbed in the metal elements which then expand and producemechanical stresses therein which tend to be concentrated at stressconcentration points, e.g., at the lower corners thereof, at region 46.

As shown in FIG. 9, since the dielectric materials do not expandsignificantly, the expansions of the metal elements initiate a rupturingat the interface 44 of the dielectric materials which separate at theinterface so as to produce a fissure which extends from one metalelement 40 to the other metal element 41, as shown by the exemplaryfissure 47. Molten metal from at least one of the metals flows throughthe fissure 47 to form a lateral conductive link between metals 40 and41.

In a particular embodiment such a lateral link was formed, betweenaluminum elements, in accordance with the technique of the inventiondiscussed with reference to FIGS. 8 and 9, using a diode-pumped Q-switchlaser, such as those made and sold by Spectra Physics Laser DiodeSystems, Inc. of Mountainview, Calif. under Model 7000 Seriesdesignation as an energy supplying source. The laser provided pulseenergy at about 400 nJ which resulted in a range of usable linkingresistances from about 0.5 ohms to about 5.5 ohms was achieved in theformation of over 30,000 links between aluminum alloy elements separatedby about 1.0 μm.

While aluminum, or alloys thereof, are found to be effective for use asthe metal elements involved, any other metal materials having relativelyhigh coefficients of thermal expansion, e.g., copper or copper alloys,can also be used.

While the use of two dielectric materials having different mechanicalstrength characteristics has been discussed in the above embodiment, thesame dielectric material can be used for dielectric layers 42 and 43, solong as the materials are deposited in layers so that a distinct,interface is clearly formed therebetween. Even when the same dielectricmaterials are so used, a rupturing will tend to occur at the interface44 so as to form the desired lateral fissure.

While the dielectric interface is shown in FIGS. 8 and 9 as beingadjacent the lower surfaces of the metal elements, the interface canalso be arranged to be adjacent the upper surfaces of the metal elementsor somewhere in between such upper and lower surfaces. Rupturing and theformation of a fissure can also occur in such latter structures toprovide the desired lateral conductive link between metal elements 40and 41.

Moreover, while FIGS. 8 and 9 show the use of two dielectric materialsto form a single interface, a pair of interfaces 44 and 49 can be formedusing three layers of dielectric materials, as shown in the embodimentof FIGS. 10 and 11. The dielectrics can be different from each other orcan be substantially the same, so long as two distinct interfaces areclearly formed at region 46. In such an approach the application oflaser energy may cause a fissure to be formed at one interface beforeone is formed at the other interface. For example, a fissure 50 can beformed at upper interface 49 from the stress concentration points at theupper corners of the metal elements, prior to the formation of a fissurefrom the stress concentration points at lower interface 44, as shown inFIG. 11. Accordingly, fissure 50 will produce a conductive link betweenmetal elements 40 and 41 in substantially the same manner as discussedabove with reference to the formation of fissure 47.

A further embodiment is shown in FIGS. 12 and 13 wherein, instead offorming a dielectric interface adjacent the upper surfaces of the metalelements, as in FIG. 10, the dielectric material 43 is deposited ondielectric 48 at a level above such upper surfaces to form an interface51 at such level. When energy is applied generally to region 46 andparticularly to the opposing ends of metal elements 40 and 41,mechanical stresses are produced at the stress concentration points,e.g., at the upper corners of the metal elements, which stressesinitiating a fracturing of the dielectric material 48 which produces afissure 52 extending from the upper corners up to the level of theinterface 51 so as to be effectively confined to the region at and belowinterface 51. A rupturing at such interface also tends to occur tofurther enhance the formation of the fissure 52 particularly at and nearthe region of the interface 51. Accordingly, metal flows into suchfissure to form a lateral conductive link between metal elements 40 and41.

It is preferred that the upper layer 43 be of a harder material thanlayer 48. For example, layer 43 might be silicon nitride (Si₃N₄) and thelayer 48 might be silicon oxide (SiO₂). It is a characteristic ofmulti-layered materials that a fracture which is initiated in a hardmaterial tends to continue on through an adjacent soft material. On theother hand, a fracture which initiates in a soft material tends to bereflected by a hard material as illustrated in FIG. 13. Thus, the use ofa harder material above the softer material tends to limit the verticalextension of the link 52 and any other fractures initiated in the layer48. In fact, this feature is advantageous even where the conductive link52 does not reach the interface 51.

In another embodiment of the invention, it has been found that the useof a preformed opening, such as preformed in an upper metal layer, willpermit the formation of a conductive link between an upper metal layerand a lower metal layer without necessarily requiring a fracturing ofthe dielectric material therebetween. The use of such a preformedopening tends to focus the laser beam energy more efficiently at thelink region. As shown in FIG. 6, an upper metal element 30 and a lowermetal element 31 are enclosed by a dielectric material 32, the overallstructure being positioned on a dielectric substrate 33. An opening 34is preformed in metal element 30 prior to the application of any energythereto. A single pulse of laser power 35 applied at the region of theopening 34 can be used to cause the metal near such region to flow intothe dielectric region and to alloy with the dielectric material or toproduce a chemical reduction reaction with the dielectric material, asdiscussed above, at the region 36. Such alloying or chemical reactionprocesses cause the dielectric material to become conductive and form aconductive link between metals 30 and 31. Because a preformed opening isused, a single pulse of relatively low laser power can be used incontrast with prior art systems where the laser energy must besufficient to provide the alloying or chemical reaction processesrequired, which processes tend to result in producing an opening in theupper metal element 30.

Alternatively, if an alloying or chemical reaction process is not used,the use of such preformed opening permits the laser energy to be focusedmore effectively at the dielectric material so as to remove suchmaterial in the region under the opening to expose the laser metal layerto form a crater 37. The laser energy also causes the metal fromelements 30 and 31 to flow along the sides of the crater that is soformed, as shown in FIG. 7.

FIGS. 14 and 15 depict an embodiment of the invention wherein a firstpattern of first conductive elements 110 of the first pattern is formedat a first level 111 of a dielectric substrate 112. Two such conductiveelements 110 are shown in FIG. 14 as extending along the same direction,i.e., they are essentially parallel to each other. It is clear that FIG.14 shows only a representative portion of an overall array of such apattern, the representative portion being along one edge 112A of thesubstrate, for example, while the overall array extends well beyond thatshown in the figure in the directions shown by arrows 113. In theparticular embodiment depicted, a second pattern of second conductiveelements 14 extends in a direction generally orthogonal to the directionof first conductive elements 110, portions 114A of each of which lie ata second level 115 below that of the first level 111. Portions 114B ofthe second conductive elements 114 lie at the same level 111 as thefirst conductive elements 110, portions 114A and the portions 114B beinginterconnected by preformed vertical vias 116 at appropriate sidesextending between levels 111 and 115 (FIG. 15). The second conductiveelements 114 are, in the particular embodiment depicted, formed in agenerally zig-zag configuration at second level 115 in order to providefor a relatively high density of elements and to permit “cuts” in theconductive elements to be made more readily, as discussed below.Portions 114B, in the embodiment depicted, effectively provideconductive portions, or tabs, at the first level 111 which areeffectively parallel to portions of conductive elements 110 that areadjacent thereto.

Using the particular configuration depicted in the embodiment of FIGS.14 and 15, for example, a plurality of conductive paths can be formed asdesired by making suitable lateral conductive links at the same level111 between selected ones of the conductive elements and, if necessary,by making appropriate cuts at selected regions of selected ones of theconductive elements.

One exemplary embodiment of the formation of a conductive path isillustrated in FIG. 16, wherein lateral links 120 and 121 are formedbetween a first conductive element 110 and adjacent tab portions 114B ofa second conductive element 114 so that a conductive path shown by theshaded regions in the figure is formed between the points thereofdepicted by arrows 125. In addition, a cut is made at region 122 of theadjacent first conductive element 110 to isolate such path from otherconductive paths that may be formed. The use of the two lateral links120 and 121 using tab portions 114B at the same level as conductiveelement 110, as shown, provides for redundancy in the conductive path soas to increase the current carrying capacity and the reliability of thepath that has been formed. Alternatively, only a single element tabportion 114B may be made available and its associated tab portion asshown in FIG. 16 may be eliminated from the original pattern, in whichcase the conductive elements can be more densely positioned on thesubstrate. In such case, however, redundant links 120 and 121 cannot beformed so that, while an increased density can be achieved, it isattained at the expense of a possible decrease in reliability.

Another exemplary conductive path shown by the shaded regions betweenarrows 126 is also depicted in FIG. 16 wherein lateral links 127 and 128are formed at the same level 111 between a first conductive element 110and adjacent portions 114B of a second conductive element 114. Anappropriate cut is made at region 129 of first conductive element 110 toisolate the conductive path from other conductive paths that may beformed.

The above described conductive paths are exemplary only and it would beclear to those in the art from such description as to how otherappropriate links and cuts can be used to form a plurality of differentconductive paths in an overall array of first and second patterns ofconductive elements preformed in a substrate, only a part of which isillustrated in FIGS. 14-16.

A further embodiment of the invention is depicted in FIG. 17 wherein thefirst and second patterns of conductive elements involved lie at thesame level in a substrate. Thus, a first pattern of first conductiveelements 140 are positioned to lie generally in the same direction and asecond pattern of second conductive elements 141 are positioned at thesame level to lie in the same general direction so that the conductiveelements of each pattern are arranged in an interdigital manner, asshown. Appropriate lateral links between selected ones of the conductiveelement 140 and 141 can be formed at the same level so as to form aplurality of conductive paths as desired, suitable cuts being also madeto isolate the paths from each other. For example, as shown in FIG. 18,appropriate links 142 and 143 are formed at the same level to provide aconductive path shown by the shaded regions between arrows 145, whileappropriate links 146 and 147 are formed at the same level to provide aconductive path shown by the shaded region between arrows 149. Suitablecuts as shown at regions 150, 151, 152, 153, and 154 are also providedto isolate such paths from each other. It is clear that FIGS. 17 and 18depict only a part of an overall array of patterns of conductiveelements 140 and 141 and it would be clear to the art from the abovedescription that a number of conductive paths could be formed in such anoverall array using appropriate lateral links at the same level, as wellas suitable cuts as required to isolate the paths from each other.

While the particular embodiments of the invention discussed above arepreferred, modifications thereto may occur to those in the art withinthe spirit and scope of the invention. Hence, the invention is not to beconstrued as limited to the specific embodiments discussed, except asdefined by the appended claims.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A device having one or more conductive paths comprising: a first conductive element preformed on a substrate in a first plane; a second conductive element preformed on said substrate in a second plane displaced from the first plane, the second conductive element being laterally displaced from the first conductive element so that the first and second conductive elements do not have an overlapping region in a plain view of the substrate; an insulating material between the first and second conductive elements and having at least one fissure therethrough between the conductive elements, the at least one fissure including a fissure having a longitudinal axis between the first and second conductive elements which includes a lateral component between the first conductive element and the second conductive element; and one or more conductive links between selected ones of said first and second conductive elements, said one or more conductive links consisting essentially of the same conductive material as at least one of the conductive elements and being in the fissures through the insulating material between the first and second conductive elements.
 2. A device in accordance with claim 1 wherein the conductive links are formed between metals.
 3. A device in accordance with claim 1 wherein said one or more conductive links are formed at fissures which extend from an edge or from near an edge of at least one of said first and second conductive elements.
 4. A device having one or more conductive paths comprising: a first conductive element; a second conductive element over the first conductive element, the second conductive element having an opening therein which is wider than and substantially covering the first conductive element, the first and second conductive elements being metal; an insulating material between the first and second conductive elements; and a link between the first and the second conductive elements resulting from a beam directed through the opening, the conductive link consisting essentially of the same conductive material as at least one of the conductive elements, being in a fissure through the insulating material between the first and second conductive elements, and extending from an edge or from near an edge of at least one of the first and second conductive elements, the fissure having a lateral component. 